The first gas-lit traffic light was installed outside the Houses of Parliament in London in 1868. It exploded less than a month later, injuring the police officer operating it. (The lesson: gas and glass lenses do not mix.)
So the next time you see that scarlet orb staring down at you from the intersection, do not see a delay. See history. See biology. See safety.
Interestingly, studies using eye-tracking technology show that drivers rarely look at the traffic light during the last 50 feet before an intersection. Instead, they look at the car in front of them. This "lead car" effect means that if the car ahead runs the red, three cars behind them are statistically likely to follow, even if their own view of the signal shows red. Red Lights
As we enter the era of autonomous vehicles (AVs) and Vehicle-to-Everything (V2X) communication, the physical red light bulb may become obsolete.
Every day, billions of people around the world face a silent, universal command. It does not speak, yet we obey it without question. It is the red light. The first gas-lit traffic light was installed outside
: Use a bottle cap or glass to trace perfect circles. 2. DIY Red Safelight Filter
For a more advanced "working" red light, you can build a paper circuit. See history
The answer lies in physics and evolution. Red light has the longest wavelength in the visible spectrum. This means it scatters less than other colors when passing through the atmosphere. On a foggy night in London or a dusty prairie, red light travels the farthest distance before degrading. It is the color of maximum visibility at range.